Light sensitive elements for color photography



Aug. 7, 1951 A. B. JENNINGS 2,563,469

LIGHT SENSITIVE ELEMENT FOR COLOR PHOTOGRAPHY Filed Feb. 18, 1947 FIG.].

o-SULFOBENZALDEHYDE-POLYVINYL ALCOHOL FINELY DIVIDED BLUE PIGMENT PAPERSUPPORT 3 ACETAL LAYER 2 '{GELATIN SILVER HALIDE LAYER CONTAINING FIGQZ.

6 CASEIN-GELATIN LAYER ryggggfifigfi GELATIN SILVER HALIDE LAYERCONTAINING 5 wilflll/mli FINELY DIVIDED YELLOW PIGMENT 4 PAPER SUPPORTFIG.'5.

9 wATER-soLuaLE METHYLCELLULOSE LAYER 8 LM LLLLL L L; GELATIN SILVERHALIDE LAYE'R CONTAINING I I FILM BASE INVENTOR. A NDRE w'BRA DSHAWJENN/NGS A TTORNEY.

Patented Aug. 7, 1951 LIGHT SENSITIVE ELEM NTSFOR. cohort PHOTOGRAPHYAndrew Bradshaw J ennings; New Brunswick, N. J assignor to E. I. du Pontde Nemours 8: Company, Wilmington, Del., a corporation .01.

Delaware Application February 18, 1947, Serial No. 729,397

2 Claims. (01. 95 -8) This invention relates to photography and, moreparticularly, to light-sensitive elements for color photography. Stillmore particularly it relates to photographic elements bearing pigmentedlight-sensitive silver halide layers which can be processed to formtransferable pigment images. The invention also relates to processes ofproducing pigment images from such elements.

An object of this invention is to provide improved elements for theproduction'of pigmented images. A further object is to providelightsensitive photographic elements which have protected pigmentedlayers. A still further object is to provide such elements which are notdeleteriously affected by photographic development 01' the silver halidelayers. will be apparent from the following description of theinvention.

The novel photographic elements of this invention consist of a film,plate, or paper support which has superimposed thereon a gelatino-silverhalide emulsion layer having intimately dispersed therethrough finelydivided inert colored pigment particles, which layer bears a protectivecoating composed of a water-soluble, dilute alkali-insoluble,film-forming colloid. The useful colloids are freely water-permeable butinsoluble in aqueous alkaline developer solutions containing 2% or moreby weight of dissolved inorganic salts.

The outer coating protects the pigmented layer during handling anddevelopment of the photographic elements but it can be readily removedwhen it is desirable to prepare for transfer the pigmented image whichis formed in the inner layer. 'The elements are exposed to light from anobject field, e. g., light from a color separation negative, whereby alatent image is formed in the silver halide layer. They are thendeveloped in an alkaline photographic developing bath whereby a silverimage of good contrast forms in the silver layer. After fixing andwashing, the elements are dried and then bleached in a hardening bleach.Each bleached component is rinsed briefly, squeegeed face down on asemirigid transparent support, such as methyl methacrylate sheets,cellulose acetate sheets, etc. After remaining in contact for a fewminutes, each combination is immersed in warm water (110- 120 FL). Theunhardened, pigmented colloid Softens, its original support is removed,and ex-* cess softened colloid is washed away in the warm water leavingpigmented relief images. The images may be transferred to othertransparent Still other objects or opaque support in known manneranalogous to that practiced in the process known as carbon printing."Alternatively, a hardening developer may be used whereby no hardeningbleach step is necessary. Similarly, relief images may be created onmetal surfaces whereby a resist is. formed for use in photomechanicalprocesses.

Various water-soluble, dilute alkali insoluble colloids-are known whichare freely permeable to photographic developing, bleaching, and fixingsolutions. Among such materials are the low substituted methyl and ethylcellulose ethers. gelatin-casein mixtures, polyvinyl alcohol andpolyvinyl alcohol acetals of aldehydes which contain SOaM or COOMgroups, where M is hydrogen or a water-soluble cation, e. -g., sodium,potassium, ammonium, tetramethylammonium, morpholine, etc.

Colloids which are especially suitable are the polyvinyl acetals ofaromatic monoaldehydes having sulfonic acid or carboxylic acid groups.Suitable acetals of this type can be prepared from polyvinyl alcoholsand substantially completely hydrolyzed polyvinyl esters and aldehydecarboxylic or sulfonic acids, such as phthalaldehydic acid, ortho-,meta-, and para-benzaldehyde sulfonic acid, acetaldehyde disulfonicacid, naphthaldehyde. sulfonic acids, e. g., l-naphthaldehyde 2 sulfonicacid, 1 naphthaldehyde 4 sulfonic acid, 2 naphthaldehyde 5 sulfonicacid, and the corresponding carboxylic acids, by condensation in thepresence of mineral acids or acid salts after the manner described inGerman Patent No; 643,650. Such acetals are insoluble in aqueousalkaline photographic developer solutions containing 2% or more byweight of dissolvedino'rganic salts. The condensation should be carriedout until the vinyl alcohol groups have been acetalizedto confer suchsolubility characteristics. The latter acetals possess a high resistanceto solubilization by alkaline photographic developer solutions andacquire a hardened surface during development of the exposed silverhalide layers.

The gelatino-silver halide emulsion layers can be prepared in the usualmanner and the finely divided inert pigments added to the emulsion atany time but preferably-atthe time it is prepared for coating. Apractical method is to disperse the pigment in an aqueous solution ofgelatin with the aid of a wetting or dispersing agent and theresultinggelatin solution is added to the gelatin silver halide emulsionand the fiowable emulsion; isccoatedxinthe usual manner onto a support,e. g., a transparent film or paper or onto a layer of soft gelatin onthe support, and dried. The pigments can be dispersed by mechanicalcomminution or grinding in a ball mill in the presence of the colloid bythe aid of wetting agents until they have an average particle size ofnot more than 1 ,u and not less than 0.1 p. in diameter. Difierentcolored pigments may be used for producing individual images of anydesired shade or alternatively blue-green, yellow, and magenta are usedin difierent elements whereby composite multicolored pictures can bemade from color separation negatives. The pigment particles maypreferably be dispersed nie-' chanically in comminuting and colloid millapparatus of known type or colloido-chemically, preferably by the use ofwetting and dispersing agents. Suitable wetting agents include alkalimetal salts, e. g., sodium and potassium salts of n-alkane sulfuric acidesters and sulfonic acids of 8 to 18 carbon atoms, the alkali metalsalts of alkylated naphthalene sulfonic acids, the N-alkyl and C-alkylbetaines wherein the alkyl .groups contain 8 to 18 carbon atoms, andwetting agents of. non-ionic type, e; g., the polyethylene glycolscontaining 8 or more ethylene units and their alkyl ethers andcarboxylic acid esters, for example, nonaand dodecaethylene glycol andtheir monoand (ii-methyl and ethyl ethers, and the hexitan derivatives,e. g., the polyoxyl alkylene ethers and esters of United StateszPatent2,440,532.

The protective coatings can be -deposited:;on the pigmented gelatinsilver halide from an aqueous solution of the water-soluble, dilutealkaliinsoluble colloids in the same manner in which emulsion,anti-abrasion, etc. layers are coated. The layers or coatings are thendried.

The invention will be further illustrated but is not limited by thefollowing examples. The parts are by weight.

Example I o-Sulfobenzaldehyde acetal of polyvinyl alcohol -gram lEthanol cc Water cc 20 and the resulting solution was coated onto thesilver halide layer to form a protective layer 3 having a coating weightof 20 milligrams per square decimeter.

The element is then processed as follows: Each pigmented element isexposed to its appropriate color record, such as a set of tricolor 'separation negatives, and developed for 2 to 5 minutes in a developer of thefollowing composition:

N-methyl-p-aminophenol sulfate grams 5.0 Na2SO3 do 60.0 Hydroquinone do7.5 NazCO-a dO 50.0 KBr do 4.5 Water to liter" 1.0

After quick rinsing the element is fixed in the 4 followingnon-hardening fixer, thoroughly and dried:

then washed Sodium thiosulfate grams..- 240.0 Sodium sulfite do 10.0sodium bisulfite do 25.0 Water to liter 1.0

After drying, the individual element isprocessed to a pigmented reliefimage as follows:

Each element is soaked for 1% minutes in the prepared bleach, rinsed forone minute, then squeegeed face down onto a freshly cleaned transparentsheet of methyl methacrylate or cellulose acetate, etc. which issomewhat larger than the paper elements. After standing in contact forfive minutes, the sandwiches are immersed water at l00-105 with thepaper-backingside of the sandwiches uppermost; f

After about one minute, the unhardened 'colloid next to the papersupport becomes softened and the paper backing may be stripped away Theremaining unhardened, pigmented colloid may be then completely washedaway by three or four minutes further washing with mild, con-' tinuousagitation in water from 100 -1l0. There remains finally pigmented reliefimages which adhere firmly to the transparent sheets.

After drying, the component images may be successively transferred inregister to a single support in known manner.

Example II s Y A paper support 6 in Fig. 2 of the drawing is coated witha fiowable gelatino-silver; iodobromide emulsion containing 10% ofgelatin and 5% of silver bromide and one part of thiofiavine S per tenparts of gelatin to form a layer 5 having a coating weight of 175milligrams of AgBr per square decimeter. A slightly alkaline 10%solution of a mixture of ten parts of casein and one part of gelatin inequal parts ofethanol and methanol is coated onto the-silver halideemulsion layer to form outer layer 6. .jllhe element is exposed under ablue color- -separation negative which is processed in a manner similarample I.

to that described in Example Iv whereby a yellowimage record is formed.It may-be superimposed in register with the image record of Ex- EmampleIII A' cellulose acetate filmfbase 1 as shown Fig. 3 of the drawing iscoated 'withan'adueous gelatino-silv'er iodobromide emulsion having-uh?formly dispersed therethrough' finely divided' particles of HalopontPink.2BM. .The ratio of gelatin to silver is 2 to 1 by weight andonegram of'pigment is used for each five gra'msof gelatin. Theresultin'glayer 8 has a coatin weight of 200 milligrams of silverbromide per square decimeter. An aqueous solution of methyl cellulose ismade by dissolving 20 parts of methyl cellulose containing 1.3 to 2.6methoxy groups per glucose unit in 800 parts of a mixture of ethanol and90% water by weight. The resulting layer 9 is resistant to solution byaqueous alkaline photographic developers, yet can be readily andcompletely removed in water. The film is exposed under a green colorseparation negative and processed as described in Example I whereby amagenta image record is formed. The final image record when superposedin register on the other two color component records of Examples I and11 results in a multi-color picture.

Various other inert colored pigments may be substituted for thosedescribed in the above examples. The phthalocyanine dyes are quiteuseful in the emulsion layers and are commercially available in variouscolors. Suitable additional specific pigments include Monastral" FastBlue GWD, Monastral Fast Green GWD, "Luxol" Fast Blue MBS, Halopont BlueBM, Halopont Brilliant Blue 2RN, "Lithosol" Yellow HLD, Halopont BlueRNM, Halopont Violet NM, Benzidine Yellow lakes, etc.

The gelatino-silver halide emulsion layers may contain, in addition tothe colored inert pigments and the light-sensitive silver halide, e. g.,silver chlorides, silver-chloride-bromide, silver-iodobromide, etc.,various sensitizing dyes andother materials which are common in emulsionlayers.

Such additional materials include fog inhibiting agents, emulsionhardeners, emulsion preservatives, etc.

An advantage of the invention is that it provides improved elements forcolor photography. The elements are superior to those used in thepreparation of pigment image photographs because the silver halidesurfaces are protected and stress marks, abrasion marks, and the likeare avoided. The outer layer does not come off during development whichis desirable. By utilizing the relatively high order of sensitivity ofsilver salts as compared to dichromated colloids, for example, muchshorter practical ex-- posure times are possible. Physical abrasion ofsuch sensitive layers is eliminated by the remov- 6 l able anti-abrasivelayers. Presensitizing before use is not necessary, of course, as in thecase of dichromated colloids.

What is claimed is:

l. A photographic element comprising a support, a gelatin silver halideemulsion layer on said suppoit which layer has finely divided solidinert pigment particles having an average particle size of 1.0 to 0.1micron uniformly dispersed therethrough and has superimposed thereon alayer composed of a water-soluble o-sulfobenzaldehyde acetal ofpolyvinyl alcohol said acetal being insoluble in alkaline photographicdeveloper solutions containing 2% by weight'of dissolved inorganicsalts.

2. A photographic element comprising a support, an unexposedlight-sensitive gelatin silver halide emulsion layer on the support,said layer having finely divided, solid, inert pigment particlespossessing an average particle size of 1.0 to 0.1 micron uniformlydispersed therethrough and having superposed thereon a layer of anacetal of a vinyl alcohol polymer with a watersoluble aldehydecontaining a group taken from the class consisting of carboxylic acidand sulfonic acid groups but which is otherwise unsubstituted, saidacetal being insoluble in alkaline photographic developer solutionscontaining 2% by weight of dissolved inorganic salts.

ANDREW BRADSHAW JENNINGS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 314,346 Roche Mar. 24, 18851,762,935 Sheppard et al. June 10, 1930 1,954,337 Staud Apr. 10, 19342,245,218 Murray, Jr. et al. June 10, 1941 2,373,289 Brown Apr. 10, 19452.391,181 Minsk et al. Dec. 18, 1945 FOREIGN PATENTS Number Country Date442,522 Great Britain Feb. 3, 1936 482,204 Great Britain Mar. 24, 1938

1. A PHOTOGRAPHIC ELEMENT COMPRISING A SUPPORT, A GELATIN SILVER HALIDEEMULSION LAYER ON SAID SUPPORT WHICH LAYER HAS FINELY DIVIDED SOLIDINERT PIGMENT PARTICLES HAVING AN AVERAGE PARTICLE SIZE OF 1.0 TO 0.1MICRON UNIFORMLY DISPERSED THERETHROUGH AND HAS SUPERIMPOSED THEREON ALAYER COMPOSED OF A WATER-SOLUBLE O-SULFOBENZALDEHYDE ACETAL OFPOLYVINYL ALCOHOL SAID ACETAL BEING INSOLUBLE IN ALKALINE PHOTOGRAPHICDEVELOPER SOLUTIONS CONTAINING 2% BY WEIGHT OF DISSOLVED INORGANICSALTS.